The reasons why the 'dog's bollocks' are considered to be the top of the tree aren't clear. It may be linked to an associated phrase - 'stand out like a dog's balls', that is, 'outstanding', although I can find no evidence to indicate that phrase as being earlier than the 'dog's bollocks'. Dogs do enjoy licking their genitals of course but again, there's no evidence that links the coining of this phrase to that. It is most likely that this is just a nonsense phrase, coined because it sounds good. In that, it would join a long list of earlier nonsense phrases, e.g. 'the cat's pyjamas', 'the bee's knees' etc.

Origin

The word bollocks, meaning testicles has been part of the language since the 18th century, but didn't become used to mean nonsense until the early 20th century. The 'dog's bollocks' seems to have originated in Britain in the first half of the 20th century. Eric Partridge recorded it in Edition 3 of A Dictionary of Slang and Unconventional English, 1949:

"Dog's ballocks, the typographical colon-dash (:-)."

That printer's term, although graphic, didn't have any associations with excellence and probably isn't the source of term as we use it today. It is more likely that the origin lies in a late 20th century reviving of the post WWI period outbreak of exuberant coinages. At that time many nonsense terms for excellent which involved the animal world were coined - cat's pyjamas, cat's whiskers, bee's knees etc.

In the 1980s the scurrilous magazine Viz used 'dog's bollocks' frequently; for example, they used it in the title of an issue in 1989:

"Viz - The Dog's Bollocks: The Best of Issues 26 to 31."

Viz's writer's didn't coint the term though - they frequently latched on to any vaguely obscene street slang and printed it. They were preceded in print by P. Brewis et al. in Gambler (cassette tape sleeve notes), circa 1986:

"They are of the opinion that, when it comes to Italian opera, Pavarotti is the dog's bollocks."

Who coined the phrase we aren't ever likely to know - it was most probably a street slang term that became established in common usage well before it ever got into print.

Since the phrase came into use some alternatives have emerged - 'the pooches privates' and, more successfully, 'the mutt's nuts'.

In November 2005, the BBC quiz show QI broadcast linked the derivation of 'the dog's bollocks' with 'box deluxe' - supposedly a classification of children's construction sets. That is nonsense. See our page on 'bog standard' for a refutation of that assertion.